The present invention relates to an improvement of a magnetic head utilizing magnetoresistance.
The underlying principle of the magnetic heads of the type described is that the current resistance or conductivity varies in a ferromagnetic material such as permalloy when a magnetic field is applied thereto. The conventional magnetic heads utilizing magnetoresistance consist of, in general, a thin ferromagnetic sheet which is made into contact with or spaced apart by a very close distance from a magnetic recording medium transported in one direction, and a pair of current terminals attached to the thin ferromagnetic sheet and spaced apart from each other by a suitable distance in the longitudinal direction thereof for flowing the current of a predetermined magnitude through the thin ferromagnetic sheet, whereby the variation in magnetic field produced by the magnetic recording medium passing over the thin ferromagnetic sheet may be detected as the variation in voltage or resistance between the current terminals. When the narrower side surface of the thin ferromagnetic sheet is made into contact with the magnetic recording medium, the magnitude of the magnetic field produced thereby is exponentially reduced in the direction vertical to the surface of the recording medium. Therefore, when the wavelength of the signal recorded on the magnetic recording medium is short, the magnetic field is too much reduced to obtain the satisfactorily strong signal. To overcome this problem, there has been proposed a method in which one of the major surfaces of the thin ferromagnetic sheet is made into contact with the magnetic recording medium, but the abrasion and wear are so pronounced, thus resulting in a very short service life as will be described in detail hereinafter.